I foolishly trusted Mozy
For a year I backed up to Mozy, even going from one OS to another, one machine to another. I tested it every once in a while by retrieving a few files, and it worked. Then the hard disk died, and I went confidently to Mozy for a backup when I got my new hard disk. After all, I had backed up just 20 minutes before the crash!
And most of it was not there.
So I contacted Mozy. I did all the online chat stuff with the folks in various parts of the world, but they could not help. So I escalated. I'm pretty good at this tracking people down, and actually got the phone number of the US-based "super help" backup. I spent HOURS on the phone over two weeks watching their top Mac guy manipulate my computer and the Mozy downloads -- evenings, weekends, even during my workweek.
Nada. They could not make the recovery work. The Mozy software had some insurmountable errors in it.
So I took the hard disk to a disk recovery service, and for under $600 I got all my data back (except Quicken data, which, it turns out, is hidden and old and unusable by the new software... but that's another story). So now I am using Carbonite. And an external hard drive.
Just a cautionary tale from one Mozy user.